Conventionally, as a method for optically analyzing a biological fluid, an analysis method using a microdevice having fluid channels has been known. A microdevice can control a fluid by using a rotation device, and it can perform measurement of a sample solution, separation of a solid component, and transfer/distribution of a separated fluid by utilizing a centrifugal force, and therefore, it can perform various kinds of biochemical analysis.
As a device for transferring a sample solution utilizing a centrifugal force, there is a rotation analysis device shown in FIG. 23 which comprises a large-sized fluid chamber 81, a measurement chamber 82 which is connected to the large-sized fluid chamber 81 and is disposed radially outer than the fluid chamber 81, an overflow chamber 83 connected to the measurement chamber 82, a reception chamber 84 disposed radially outer than the measurement chamber 82, and a capillary tube joint means 85 for supplying a fluid from the measurement chamber 82 to the reception chamber 84.
The capillary tube joint means 85 includes a siphon 86 having a capillary tube structure, and it is positioned such that the distance from the center of the rotation analysis device to an elbow-shaped bend portion of the siphon 86 is substantially equal to the distance from the center of the rotation analysis device to a radially innermost point of the measurement chamber 82. Since the capillary tube force is smaller than the centrifugal force during rotation of the rotation analysis device, the fluid/air interface matches the shape of a rotation cylindrical body which has the same axis line as that of the rotation analysis device and has a radius as long as the distance from the center of the rotation analysis device to the radially innermost point of the measurement chamber 82, and the measurement chamber 82 is filled with the sample solution and the excessive sample solution flows into the overflow chamber 83.
When the rotation analysis device is stopped, the sample solution filled in the measurement chamber 82 flows into the capillary tube joint means 85 due to a capillary force, and the siphon starts to operate by rotating the analysis device again, and thereby the solution existing in the measurement chamber 82 is discharged to the reception chamber 84 (refer to Japanese Published Patent Application No. Hei.5-508709).
At this time, if the sample solution contains a solid component, the solid component is precipitated by performing centrifugal separation in the measurement chamber 82 or the reception chamber 84, and thereafter, the capillary tube having the siphon structure is connected to a radially inner part of the chamber, whereby only the solution component in the sample solution can be transferred to the next process.
In the above-described conventional construction, although only the solution component in the sample solution can be transferred by only adjusting the position to which the capillary tube is connected after performing the centrifugal separation, since the solid component is precipitated in the outer circumference direction, the solid component or the high-concentration solid component solution cannot be transferred by the transfer using the siphon.
Further, when only the solution component is transferred by the capillary tube having the siphon structure, the remaining solution again flows into the capillary tube with stopping of the rotation, and the solution in the capillary tube is again transferred by the next rotation, thereby adversely affecting the measurement precision due to variation in the solution amount or flow-in of the solid component into the capillary tube.